The present invention relates generally to portable combustion powered fastener driving tools, and specifically to a shield to protect a workpiece-contacting element of a nosepiece of such tools.
Portable combustion powered tools utilized for driving fasteners into workpieces are described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722, 5,197,646, 5,263,439, 5,558,264, and 5,687,899, all of which are incorporated by reference herein. Similar combustion powered nail and staple driving tools are available commercially from ITW-Paslode of Vernon Hills, Ill. under the IMPULSE.RTM. brand.
Such tools incorporate a generally pistol-shaped tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces the spark for ignition, and a fan located in the combustion chamber provides for both an efficient combustion within the chamber, and facilitates scavenging, including the exhaust of combustion by-products. The engine includes a reciprocating piston with an elongated, rigid driver rod disposed within a cylinder body.
A valve sleeve is axially reciprocal about the cylinder and, through a linkage, moves to close the combustion chamber when a work contact element at the end of the linkage is pressed against a workpiece. This pressing action also triggers a fuel metering valve to introduce a specified volume of fuel into the closed combustion chamber.
Upon the pulling of a trigger switch, which causes the ignition of a charge of gas in the combustion chamber of the engine, the piston and driver rod are shot downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original, or "ready" position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver rod. Upon ignition of the combustible fuel/air mixture, the combustion in the chamber causes the acceleration of the piston/driver rod assembly and the penetration of the fastener into the workpiece if the fastener is present.
The nosepiece of the tool includes a pair of upper and lower guide members for guiding the driver rod towards the uppermost nail of a nail strip. Fasteners are guided to the workpiece by a workpiece end of the nosepiece.
A disadvantage of conventional combustion powered tools of this type is that the nosepiece is not enclosed by the housing. Therefore, in some applications, damage can occur to the nosepiece if, for example, a workman dropped the tool. Also, the nosepiece is adjustable to vary the depth that the fastener is driven into the workpiece. These adjustments are typically made by the operator of the tool. Thus, there is a need to protect the nosepiece, and the corresponding components of the nosepiece, from external forces. There is also a need to protect the depth adjustment from inadvertent impact or interference by the operator or others.
As a consequence, it is an object of this invention to provide an improved portable combustion powered fastener driving tool with a shield to protect the nosepiece of the tool from impact.
It is a further object of the present invention to provide an improved portable combustion powered fastener driving tool with a nosepiece shield containing access openings for access to the nosepiece depth adjustment.